Method of removing carbonized oil residue from magnesium articles



' fro Patented Apr. 11, 1944 p METHOD OF REMOVING omnomzsn on.

RESIDUE FROM MAGNESIUM ARTICLES Herbert K. De Long, Midland, Mich, assignor The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing.

2 Claims.

This-invention relates to a method of cleaning articles of magnesium and magnesium-base alloys.

In certain processes for fabricating articles m magnesium and magnesium-base alloys, as by rolling. extrusion, drawing, and the like, practice occasionally demands that lubricants, usually mineral or vegetable'oils, be used to facilitate operation. These oils tend to coat the surface of the resulting articles. Then, if the article is heat treated o otherwise subjected to elevated temperatures during or after the particular fabrication process involved, the oils are, in part, decomposed or oxidized by the combined action of heat, air, and the magnesium surface, and are converted to gummy, carbonized materials, which, for present purposes, may be termed oil residues." These residues, which also may be formed when oil-coated magnesium articles are exposed-to the atmosphere for longperiods or time, tend to detract from the appearance and usefulness of the final product, and; should be removed. However, wire brushing is virtually without effect on the 011 residues, and ordinary alkaline cleaners and degreasing solvents, although they loosen the residues somewhat, do not remove them satisfactorily. I

It is therefore an object of the present invention to provide a simple, inexpensive, and effective method of removing 011 residues from articles of magnesium and magnesium-base alloys.

According to the invention, moved from magnesium and magnesium-base alloy articles by subjecting the articles to the action of an aqueous alkaline solution of a, tartrate. In so far as is known, any water-soluble salt of tartaric acid may be used in theprocess, alkali metal tartrates such as sodium tartrate, sodium bitartrate, and Rochelle salt having been found particularly suitable. The tartrate shouldpreferably be present in the solution in a concentration between about 1 and about 5 per cent by Application November 7, 1940, Serial N0. 364,691

metal hydroxides, e. g. sodium hydroxide, are greatly to be preferred. The alkaline agent is ordinarily, though not necessarily, added to the solution in a proportion between about 1 and about 5 per cent by weight.

Whilethe treating solutions ordinarily contain only the tartrate and the alkali as eiiectlve ingredients, other substances maybe added without departing from the invention. Thus, in cleaning articles having on their surface a considerable film of oil in addition to oil residues, it is desirable to add to the tartrate solution 0.5 to 2.0 per cent by weight or more of a soluble detergent, such as a soap or a salt of a suliated higher aliphatic alcohol or of a sulfonated aromatlc hydrocarbon.

' magnesium-base oil residues are reweight, although other proportions are operable,

in most instances. a

The tartratesolution may be made alkaline by any soluble basic-acting agent, although in general the stronger bases, such as trisodium phosphate, sodium carbonate, hydroxide, and the like,

tetramethyl ammonium and especially the alkali In cleaning oil-residue coated magnesium and alloy articles, it is necessary only to dip the article in the cleaning solution for a short time, and then to withdraw it and rinse it in water. When the olution is hot, as at -100 (2., a simple dip for Q5 seconds ('02 minutes suiiices to remove all, the oil residue. However, if the solution is at room temperature, strong agitation cleaned electrolytically, cathode of a cell in which solution is the electrolyte.

It is to be understood that the foregoing de scription is illustrative rather than strictly limitartrate and between about 1 and about 5 per cent of an alkali metal thereafter rinsing and drying the article.

2. The method according to claim 1 wherein thealkaline tartrate solution is maintained at a temperature 01' 90 to C. l

a rrnannar K. DE LONG. I

hydroxide, 

